Rollup merge of #126034 - ChrisDenton:winsupport, r=ehuss

Clarify our tier 1 Windows Server support

I've been asked a number of times about our minimum Windows Server support so this PR updates the documentation to be more explicit.

Note that this doesn't change our support at all, it just clarifies it. Windows Server 2016 is the first "Windows 10" server OS (specifically it has the same [build number](https://en.wikipedia.org/wiki/Windows_Server_2016#Release_to_manufacturing) as Windows 10 1607).

src/doc/rustc/src/platform-support.md

@@ -33,12 +33,12 @@ All tier 1 targets with host tools support the full standard library.
 target | notes
 -------|-------
 `aarch64-unknown-linux-gnu` | ARM64 Linux (kernel 4.1, glibc 2.17+)
-`i686-pc-windows-gnu` | 32-bit MinGW (Windows 10+) [^x86_32-floats-return-ABI]
-`i686-pc-windows-msvc` | 32-bit MSVC (Windows 10+) [^x86_32-floats-return-ABI]
+`i686-pc-windows-gnu` | 32-bit MinGW (Windows 10+, Windows Server 2016+) [^x86_32-floats-return-ABI]
+`i686-pc-windows-msvc` | 32-bit MSVC (Windows 10+, Windows Server 2016+) [^x86_32-floats-return-ABI]
 `i686-unknown-linux-gnu` | 32-bit Linux (kernel 3.2+, glibc 2.17+) [^x86_32-floats-return-ABI]
 [`x86_64-apple-darwin`](platform-support/apple-darwin.md) | 64-bit macOS (10.12+, Sierra+)
-`x86_64-pc-windows-gnu` | 64-bit MinGW (Windows 10+)
-`x86_64-pc-windows-msvc` | 64-bit MSVC (Windows 10+)
+`x86_64-pc-windows-gnu` | 64-bit MinGW (Windows 10+, Windows Server 2016+)
+`x86_64-pc-windows-msvc` | 64-bit MSVC (Windows 10+, Windows Server 2016+)
 `x86_64-unknown-linux-gnu` | 64-bit Linux (kernel 3.2+, glibc 2.17+)
 
 [^x86_32-floats-return-ABI]: Due to limitations of the C ABI, floating-point support on `i686` targets is non-compliant: floating-point return values are passed via an x87 register, so NaN payload bits can be lost. See [issue #114479][x86-32-float-issue].